1. Chapter 12
Pictorial Drawings

2. Objectives
Explain the importance of pictorial drawings as an aid in visualization
Create an isometric drawing of an object composed of principal, inclined, and oblique surfaces
Draw ellipses on the front, top, and right faces of the isometric to represent cylinders and holes

3. Objectives (cont’d.)
Explain the difference between a cavalier and cabinet oblique drawing
Create an oblique drawing given the orthographic drawing of an object
Create a two-point perspective drawing given the orientation of the plan view and the location of the elevation view

4. Introduction Pictorial drawings can help visualize a 3-D object
Also important when assembling parts into mechanisms or purchasing replacement parts
Not used as working drawings
Many types and variations

5. Axonometric Drawings
FIGURE Three visible normal surfaces (frontal, horizontal, and profile) of a prism have equal angles between them (120°) in an isometric drawing.
FIGURE In a diametric
drawing, two of the three visible
normal surfaces (frontal and
profile) of a prism have edges
presented at equal angles, not
equal to 120°.

6. Axonometric Drawings (cont’d.)
FIGURE A trimetric drawing presents the three visible normal surfaces (frontal, horizontal, and profile) of a prism in a position where none of the angles between the surface edges is equal.

7. Isometric Drawing FIGURE 12.07. The isometric axes.
FIGURE Orthographic
views of a step block.

8. Isometric Drawing (cont’d.)
FIGURE The steps to draw an isometric pictorial of the step block.

9. Inclined Surfaces
FIGURE Orthographic views of a step block with an inclined surface.

10. Inclined Surfaces (cont’d.)
FIGURE The step involved to create an isometric pictorial of a step block with an inclined surface.

11. Oblique Surfaces
FIGURE Orthographic views of a step block with an oblique surface.

12. Oblique Surfaces (cont’d.)
FIGURE The steps involved to create an isometric pictorial of a step block with an oblique surface.

13. Cylindrical Surfaces
FIGURE An isometric cube showing ellipses on each face. Note the orientation of the long (major) axis for the ellipse on each of the three normal faces.

14. Cylindrical Surfaces (cont’d.)
FIGURE Drawing an ellipse on the top isometric surface using the traditional four-center method.

15. Cylindrical Surfaces (cont’d.)
FIGURE Drawing an
ellipse on the left isometric
surface using the traditional
four-center method.

16. Ellipses on Inclined Surfaces
FIGURE Steps 1 and 2 to create an isometric pictorial showing a vertical circular hole in an inclined surface.

17. Ellipses on Inclined Surfaces (cont’d.)
FIGURE Steps 3 and 4 to create an isometric pictorial showing a vertical circular hole in an inclined surface.

18. Ellipses on Inclined Surfaces (cont’d.)
FIGURE Steps 5 and 6 to create an isometric pictorial showing a vertical circular hole in an inclined surface.

19. Ellipses on Inclined Surfaces (cont’d.)
FIGURE The finished
construction of the vertical
circular hole in an inclined
surface.

20. Oblique Drawings Types of oblique drawings
FIGURE A cabinet oblique pictorial.
FIGURE A cavalier oblique pictorial.

21. Construction of Oblique Drawings
FIGURE The steps
required to construct an oblique pictorial.

22. Construction of an Object with Circular Features
FIGURE The steps required to construct an oblique pictorial with circular features.

23. Perspective Drawings
FIGURE An illustration showing railroad tracks converging to a vanishing point on the horizon.

24. Types of Perspective Drawings
FIGURE An example of a two-point perspective drawing.

25. Types of Perspective Drawings (cont’d.)
FIGURE An example of a
three-point perspective drawing.

26. Two-Point Perspective Drawings
FIGURE The relationship between the PP and the object.

27. Construction of a Two-Point Perspective Drawing
FIGURE Establishing
and marking the left and right
vanishing points.

28. Construction of a Two-Point Perspective Drawing (cont’d.)
FIGURE Establishing the ML.

29. Construction of a Two-Point Perspective Drawing (cont’d.)
FIGURE Drawing the visual rays of the object to the PP through the SP.

30. Construction of a Two-Point Perspective Drawing (cont’d.)
FIGURE Completion of the perspective.

31. Complex Object in Two-Point Perspective
FIGURE A two-point perspective drawing of a complex object.

32. Considerations for 3-D Modeling
Easiest way to create pictorial drawings is to extract from solid models
Usually matter of specifying viewing orientation and amount of perspective
Very easy to extract

33. Summary
Used pictorial drawings for visualization and understanding 3-D relationships of objects
Created isometric drawings for simple communication

34. Summary (cont’d.)
Introduced oblique drawings, which are very quickly and simply created
Used perspective drawings for applications that demand the most realistic appearance